Voltage-controlled oscillator including plurality of delay cells

Abstract

A voltage-controlled oscillator includes a delay circuit. The delay circuit includes a first buffer inverter which receives one of the differential input signal and outputs an other of the differential output signal, a second buffer inverter which receives the other of the differential input signal and outputs the one of the differential output signal, a first latch inverter which receives the one of the differential output signal, and includes an output connected to an output of the first buffer inverter, and a second latch inverter which receives the other of the differential output signal, and includes an output connected to an output of the second buffer inverter. The first latch inverter and the first buffer inverter receive a current produced from different voltage-current conversion circuits.

1. A voltage-controlled oscillator, comprising:
 a plurality of delay cells cascade connected, each of the delay cells receiving a differential input signal and outputting a delayed differential output signal, a delay time of the delay cells being controlled by a current to be supplied from a voltage-current conversion circuit, a differential output signal of a last stage of the delay cells being fed back as a differential input signal of a first stage of the delay cells so that the differential output signal has a reversed phase with an input of the first stage of the delay cells, in order to produce an oscillation frequency controlled by applying a voltage to the voltage-current conversion circuit, wherein 
 each of the plurality of delay cells includes:
 a first buffer inverter which receives one of the differential input signal and outputs an other of the differential output signal; 
 a second buffer inverter which receives an other of the differential input signal and outputs one of the differential output signal; 
 a first latch inverter which receives the one of the differential output signal, and includes an output connected to an output of the first buffer inverter; and 
 a second latch inverter which receives the other of the differential output signal, and includes an output connected to an output of the second buffer inverter, 
 wherein the first latch inverter and the first buffer inverter receive a current produced from different voltage-current conversion circuits; and 
 wherein each of the plurality of delay cells includes: 
 a first voltage-current conversion circuit which supplies a first current to the first buffer inverter; 
 a second voltage-current conversion circuit which supplies a second current to the second buffer inverter; 
 a third voltage-current conversion circuit which supplies a third current to the first latch inverter; and 
 a fourth voltage-current conversion circuit which supplies a fourth current to the second latch inverter. 
 
 
     
     
       2. The voltage-controlled oscillator according to  claim 1 , wherein the first to fourth voltage-current conversion circuits comprise:
 a first current-source transistor of a first conductivity type, including a source connected to a first power supply node, a gate connected to a first reference voltage node, and a drain connected to the first buffer inverter; 
 a second current-source transistor of a second conductivity type, including a source connected to a second power supply node, a gate connected to the second reference voltage node, and a drain connected to a source of the first buffer inverter; 
 a third current-source transistor of the first conductivity type, including a source connected to the first power supply node, a gate connected to the first reference voltage node, and a drain connected to the second buffer inverter; 
 a fourth current-source transistor of the second conductivity type, including a source connected to the second power supply node, a gate connected to the second reference voltage node, and a drain connected to the second buffer inverter; 
 a fifth current-source transistor of the first conductivity type, including a source connected to the first power supply node, a gate connected to the first reference voltage node, and a drain connected to the first latch inverter; 
 a sixth current-source transistor of the second conductivity type, including a source connected to the second power supply node, a gate connected to the second reference voltage node, and a drain connected to the first latch inverter; 
 a seventh current-source transistor of the first conductivity type, including a source connected to the first power supply node, a gate connected to the first reference voltage node, and a drain connected to the second latch inverter; and 
 an eighth current-source transistor of the second conductivity type, including a source connected to the second power supply node, a gate connected to the second reference voltage node, and a drain connected to the second latch inverter. 
 
     
     
       3. A voltage-controlled oscillator, comprising:
 a plurality of delay cells cascade connected, each of the delay cells receiving a differential input signal and outputting a delayed differential output signal, a delay time of the delay cells being controlled by a current to be supplied from a voltage-current conversion circuit, a differential output signal of a last stage of the delay cells being fed back as a differential input signal of a first stage of the delay cells so that the differential output signal has a reversed phase with an input of the first stage of the delay cells, in order to produce an oscillation frequency controlled by applying a voltage to the voltage-current conversion circuit, wherein 
 each of the plurality of delay cells includes:
 a first buffer inverter which receives one of the differential input signal and outputs an other of the differential output signal; 
 a second buffer inverter which receives an other of the differential input signal and outputs one of the differential output signal; 
 a first latch inverter which receives the one of the differential output signal, and includes an output connected to an output of the first buffer inverter; and 
 a second latch inverter which receives the other of the differential output signal, and includes an output connected to an output of the second buffer inverter, 
 wherein the first latch inverter and the first buffer inverter receive a current produced from different voltage-current conversion circuits, and 
 
 wherein each of the plurality of delay cells includes: 
 a first voltage-current conversion circuit which supplies a first current to the first and second buffer inverters; and 
 a second voltage-current conversion circuit supplying a second current to the first and second latch inverters. 
 
     
     
       4. The voltage-controlled oscillator according to  claim 3 , wherein the first and second voltage-current conversion circuits comprise:
 a first current-source transistor of a first conductivity type, including a source connected to a first power supply node, a gate connected to a first reference voltage node, and a drain connected to sources of the first and second buffer inverters; 
 a second current-source transistor of a second conductivity type, including a source connected to a second power supply node, a gate connected to a second reference voltage node, and a drain connected to the first and second buffer inverters; 
 a third current-source transistor of the first conductivity type, including a source connected to the first power supply node, a gate connected to the first reference voltage node, and a drain connected to the first and second latch inverters; and 
 a fourth current-source transistor of the second conductivity type, including a source connected to the second power supply node, a gate connected to a second reference voltage node, and a drain connected to the first and second latch inverters. 
 
     
     
       5. A voltage-controlled oscillator including a plurality of delay cells, connected in series,
 each of the plurality of delay cells comprising: 
 a first buffer inverter which receives a differential input signal and outputs a differential output signal; 
 a second buffer inverter which receives an other of the differential input signal and outputs one of the differential output signal; 
 a first latch inverter which receives the one of the differential output signal, and includes an output connected to an output of the first buffer inverter; and 
 a second latch inverter which receives the differential output signal, and includes an output connected to an output of the second buffer inverter, 
 a first voltage-current conversion circuit which outputs a first current to apply the first current to the first latch inverter; and 
 a second voltage-current conversion circuit which outputs a second current to apply the second current to the first buffer inverter; 
 said delay cells further comprising: 
 a third voltage-current conversion circuit which outputs a third current to apply the third current to the second latch inverter; and 
 a fourth voltage-current conversion circuit which outputs a fourth current to apply the fourth current to the second buffer inverter. 
 
     
     
       6. The voltage-controlled oscillator as claimed in  claim 5 , wherein the first and second voltage-current conversion circuits include a common first transistor, and the third and fourth voltage-current conversion circuits include a common second transistor. 
     
     
       7. The voltage-controlled oscillator as claimed in  claim 5 , wherein the first to fourth voltage-current conversion circuits include first to fourth transistors, respectively. 
     
     
       8. The voltage-controlled oscillator as claimed in  claim 5 , wherein the first and third voltage-current conversion circuits include a common first transistor, and the second and fourth voltage-current conversion circuits include a common second transistor.